Because of their weight economy, strength, and stylishness, aluminum alloy extrusions have grown in popularity for the wheel rims of racing, touring and special event bicycles; and one widely used prior art scheme for interconnecting the cut ends of a rim extrusion has employed a pair of solid steel pins which are force-fit into the confronting ends of spaced-apart tubulations extruded into the rim cross-section. It has also been common practice heretofore to provide the tubulations with a non-round shape, such as triangular or elliptic, in order to avoid or ameliorate the creation of unsightly bulges on the rim sidewalls where the pins are pressed into the tubulations. However, the round pins do not fit completely into such tubulations, leaving one or more narrow channels communicating past the pins and into the annular spaces of the tubulations. Anodizing solutions applied to the completed rim after assembly have been found to invade the tubulations through these channels during chemical processing and to leak out later in retrograde flow. Unsightly staining of the anodized finish has resulted; and this has proved especially objectionable with regard to intense-color anodizations such as black, gold, red or blue treatments.